Atrial fibrillation (AF), a heart rhythm problem in which the atria (upper chambers of the heart) stop contracting as they fibrillate or quiver, is the most common of all the heart rhythm problems. It is estimated that over 2.2 million patients in the U.S. have AF and over 140,000 new cases are diagnosed every year. Patients with AF have a high risk of stroke. The Framingham Study demonstrated that the diagnosis of AF increased the risk of stroke 3 to 5 times higher and the risk rose from 1.5 percent during the fifth decade of life to over 23% by the eight decade.
More specifically, previous studies have indicated that more than 90 percent of AF related strokes result from a blood clot that forms in the left atrial appendage (LAA), a small pouch-like structure in the left atrium. Such blood clots can dislodge from the atrium and travel to the brain, thereby causing a stroke. Several large trials have shown the efficacy of warfarin, a blood thinner, in reducing the risk of stroke. In clinical practice, however, the warfarin is contraindicated or cannot be used because of side effects such as bleeding in over 40 percent of patients.
In addition to the LAA being a source of blood clots it can also play a role in the initiation and maintenance of AF. In treating AF, lesions are placed at strategic locations to prevent the conduction of errant electrical impulses. The LAA appendage is routinely removed in a surgical procedure for treating AF called the MAZE procedure. The removal of the LAA has been recommended by the American College of Cardiology-American Heart Association guidelines.
Recently, a catheter technique call PLAATO (percutaneous left atrial appendage trans catheter occlusion) has been tried as a blocking device from the inside of the left atrial chamber. In one study of this technique, the catheter implant sizes ranged significantly, the procedure time ran over 90 minutes and, in 25 percent of these patients, the initial device required removal and replacement with a device of a different size. There was also additional risk of bleeding around the heart, a complication that can at times be life-threatening.
There is thus a need for a method and system for establishing an effective road map of the LAA. There is also a need for a method and system for isolating the LAA that uses a minimally-invasive approach not going inside the left atrial chamber. Such a method and system would eliminate the need for different size catheters and reduce the risk of complications, thereby providing an alternative strategy for the prevention of stroke and the treatment of AF.
It is an object of this invention to provide an improved catheter apparatus for use in the isolation of the LAA that overcomes some of the problems and shortcomings in the prior art, including those referred to above.